The present invention relates to an electrode connecting method, a narrow-pitch connector with terminals connected by this connecting method, a pitch converter, a micro-machine, a piezoelectric actuator, an electrostatic actuator, an ink jet head, an ink jet printer, a liquid crystal device, and electronic equipment.
Recently, electronic equipment has been developed remarkably, and the degree of integration per unit area has been enhanced as the electronic equipment has been made smaller in size, lighter in weight and larger in capacity. In the present circumstances, however, the technical advance of peripheral portions of the electronic equipment lags behind relatively, and there is no proposal particularly to make terminal electrodes of a connection portion finer.
Connecting subjects such as printer heads (hereinafter referred to as xe2x80x9cprinter engine portionsxe2x80x9d) having piezoelectric elements for blasting ink by the vibration of the piezoelectric elements, LCD cells of liquid crystal devices, or the like, have been made finer year by year, so that the interval between terminal electrodes has become narrower correspondingly. To connect a driving circuit to such a connecting subject, a connector constituted by a flexible substrate is hitherto attached to convert the pitch of a wiring pattern so as to make a connection with the driving circuit.
This connection will be described in detail with reference to the drawings. FIG. 17 is a main portion enlarged view of a connecting subject and a connector constituted by a flexible substrate. As shown in FIG. 17, in a connecting subject 1 such as a printer engine portion, an LCD cell of a liquid crystal device, or the like, a plurality of wirings 2 connected with elements are drawn around on the surface of the connecting subject 1, and terminal electrodes 3 are formed in end portions of the connecting subject 1.
On the other hand, a connector 4 for making a connection with the connecting subject 1 is formed of a flexible substrate the material of which is composed of polyimide. Terminal electrodes 5 which can be put on the terminal electrodes 3 respectively formed in the end portions of the connecting subject 1 are formed at one end of this substrate while terminal electrodes 6 which are wider than the terminal electrodes 5 and which are disposed at larger intervals than the terminal electrodes 5 are formed in the end portion opposite to the terminal electrodes 5. Wirings 6A are provided to connect the terminal electrodes 5 with the terminal electrodes 6 so that the width and intervals are changed on the way where the wirings 6A are drawn around.
FIG. 18 is an explanatory view showing the process of connecting the connecting subject 1 with the connector 4. As shown in FIG. 18, in the case where the aforementioned connecting subject 1 and the aforementioned connector 4 are connected with each other, the connecting subject 1 is first disposed on a bonding stage 7 so that the terminal electrodes 3 are located on the upper surface side. Next, positioning is performed between the terminal electrodes 5 provided on the connector 4 and the aforementioned terminal electrodes 3 so that both the terminal electrodes are put on top of each other. Incidentally, a bonding agent containing electrically conductive particles are applied between the terminal electrodes 3 and the terminal electrodes 5 so that both the terminal electrodes are made electrically conductive with each other through the electrically conductive particles.
Here, a bonding tool 8 which can move up and down is provided above the position where both the electrodes are put on top of each other, that is, above the terminal electrodes 5 in the connector 4. Incidentally, the bonding tool 8 includes a heater 9 so that a front end portion of the bonding tool 8 can be heated by operating this heater 9.
By moving down the bonding tool 8 configured thus, both the electrodes are connected with each other while not only is it intended to bring both the electrodes into close contact with the electrically conductive particles but also it is intended to shorten the time to dry the bonding agent by heating. Incidentally, when both the electrodes are connected with each other, the bonding agent containing electrically conductive particles is not always required. Both the electrodes may be welded or metal-bonded by applying pressure and heat to the electrodes which are put on top of each other without any bonding agent therebetween.
Incidentally, although a printer head (printer engine portion) using a piezoelectric element or an LCD cell of a liquid crystal device was described here by way of example, bonding may be performed by a similar technique also in a micro-machine in which a fine moving mechanism portion is formed on a substrate and a wiring for transferring energy (for applying a voltage) to this moving mechanism portion is extracted, a piezoelectric actuator using a piezoelectric element, an electrostatic actuator using an electrostatic vibrator, a printer head using an electrostatic actuator, a printer using such an actuator, and electronic equipment mounted with such apparatus.
However, in the connector or the electrode connecting method described above, there have been technical problems as follows.
FIGS. 19(a) and (b) show sectional views respectively taken on line Cxe2x80x94C in FIG. 18, in which a interval 10 between the terminal electrodes 3 is made narrower correspondingly to the fact that the connecting subject 1 such as a printer engine portion, an LCD cell of a liquid crystal device, or the like, has been made finer year by year as described above. As a result, if the material composing the connecting subject 1 (mainly silicon) and the material composing the connector 4 (mainly polyimide) are different in thermal expansion coefficient, the thermal expansion of the connector 4 becomes larger due to the influence of the heater 9 included in the bonding tool 8 when the bonding tool 8 is made close to the connecting subject 1 and the connector 4 in order to bond them. As a result, as shown in FIG. 19(b), the terminal electrodes 5 are displaced relatively to the terminal connectors 3 respectively. Thus, there has been a fear that there arises a problem such as increase in resistance value or failure in bonding between both the terminals, or short-circuit with adjacent terminals. Incidentally, according to various investigations made by the present inventor, it was confirmed that there was a limit of a wiring pitch near 60 xcexcm in a connector made of polyimide material.
On the other hand, in the electrode connecting method, heating when both the terminals are connected with each other is performed by the heater 9 included in the bonding tool 8. However, if heating is performed by the heater 9, the temperature of the connector 4 becomes higher than that of the connecting subject 1 so that there arises a temperature difference between the connecting subject 1 and the connector 4. If the thermal expansion coefficient of the material composing the connector 4 is larger than that of the material composing the connecting subject 1, the deviation of the terminal electrodes 5 from the terminal electrodes 3 when both the terminal electrodes are connected with each other increases still more. According to various investigations made by the present inventor, it was confirmed that the temperature was in a range of from 360xc2x0 C. to 400xc2x0 C. at a position a, in a range of from 180xc2x0 C. to 230xc2x0 C. at a position b, and about 160xc2x0 C. at a position c.
Incidentally, in an actuator, or the like, manufactured by use of a micro-machine or micro-machining technique, the area of wiring terminals increases in comparison with a moving mechanism portion or an actuator portion because the actuator is connected with an external board by a method of flexible-substrate or wire bonding, wire cable soldering, or the like. In order to form such a moving mechanism portion or actuator, precise machining represented by anisotropic etching is required, and an expensive material or an expensive machine is also required. It is therefore desired that the area of wiring terminal portions is made so minimal that the moving mechanism portion or actuator is manufactured efficiently.
It is an object of the present invention to provide an electrode connecting method in which, even if terminal electrodes of connecting subjects having different thermal expansion coefficients are connected with each other, the positional deviation between these terminal electrodes to be connected with each other can be restrained; and a narrow-pitch connector in which the positional deviation between terminal electrodes to be connected with each other can be reduced even if thermal stress is applied; a pitch converter; a micro-machine; a piezoelectric actuator; an electrostatic actuator; an ink jet head; an ink jet printer; a liquid crystal device; and electronic equipment.
(1) According to an aspect of the present invention, there is provided a narrow-pitch connector in which a plurality of first terminal electrodes and a plurality of second terminal electrodes are formed on a substrate, and wiring is formed for electrically connecting the first terminal electrodes with the second terminal electrodes; wherein the wiring has a function of making a conversion from a pitch of the first terminal electrodes to a pitch of the second terminal electrodes.
(2) According to another aspect of the present invention, in the narrow-pitch connector stated in the above paragraph (1), the substrate is formed of silicon.
(3) According to another aspect of the present invention, in the narrow-pitch connector stated in the above paragraph (1), the first terminal electrodes are arranged so that the pitch of the first terminal electrodes is set to be not larger than 60 xcexcm.
(4) According to another aspect of the present invention, in the narrow-pitch connector stated in the above paragraph (1), the second terminal electrodes are arranged so that the pitch of the second terminal electrodes is set to be not smaller than 80 xcexcm.
(5) According to another aspect of the present invention, in the narrow-pitch connector stated in the above paragraph (1), the second terminal electrodes are terminal electrodes for making a connection with a flexible substrate such as a flexible board, a tape carrier package, or the like.
In the aforementioned inventions (1) to (5), the substrate of the narrow-pitch connector for making a conversion from the pitch of the first terminal electrodes to the pitch of the second terminal electrodes by the wiring is formed of silicon. Accordingly, the connector can have a small thermal expansion coefficient and be formed in the same manner as the process for forming a semiconductor device. Therefore, the wiring can be easily formed with a narrow pitch.
In addition, the terminal pitch of the first terminal electrodes of the narrow-pitch connector is set to be not larger than 60 xcexcm. Such terminal electrodes with a narrow pitch not larger than 60 xcexcm cannot be formed in any background-art connector, but can be attained for the first time by the narrow-pitch connector according to the present invention.
Further, the terminal pitch of the second terminal electrodes of the narrow-pitch connector is set to be not smaller than 80 xcexcm. By extending the terminal pitch of the second terminal electrodes to be not smaller than 80 xcexcm thus, the terminal pitch of the second terminal electrodes can be easily adjusted to that of the terminals on the side of a flexible-substrate such as a flexible board, a tape carrier package, or the like, and a stable connection can be made with such a flexible substrate.
(6) According to another aspect of the present invention, there is provided a pitch converter which comprises: a narrow-pitch connector in which a plurality of first terminal electrodes and a plurality of second terminal electrodes are formed on a substrate, and wiring is formed for electrically connecting the first terminal electrodes with the second terminal electrodes; and a connecting subject having external electrodes which are to be electrically connected with the first terminal electrodes.
(7) According to another aspect of the present invention, in the pitch converter stated in the above paragraph (6), the substrate has a characteristic that a thermal expansion coefficient thereof is substantially equal to or smaller than a thermal expansion coefficient of the connecting subject.
(8) According to another aspect of the present invention, in the pitch converter stated in the above paragraph (6), the substrate and the connecting subject are formed of the same material.
(9) According to another aspect of the present invention, in the pitch converter stated in the above paragraph (6), the substrate and the connecting subject are formed of silicon.
(10) According to another aspect of the present invention, in the pitch converter stated in the above paragraph (6), the first terminal electrodes are electrically connected with the external electrodes through electrically conductive members.
In the aforementioned inventions (6) to (10), the substrate of the narrow-pitch connector has a characteristic that the thermal expansion coefficient of the substrate is substantially equal to or smaller than that of the connecting subject. Accordingly, when the first terminal electrodes of the connector and the external electrodes of the connecting subject are connected with each other by pressing and heating, both the electrodes are lengthened by substantially the same quantity so that the relative positional deviation of the electrodes which are put on top of each other can be restrained to the minimum.
In addition, because the substrates of the narrow-pitch connector and the connecting subject are formed of the same material, the relative positional deviation of the electrodes can be restrained when the electrodes are put on top of each other.
Further, because silicon which is high in heat conductivity is used as the material of the substrate of the narrow-pitch connector and the connecting subject, the effect of heat radiation can be more enhanced so that the resistance value can be prevented from increasing due to temperature rise.
Moreover, because the first terminal electrodes of the connector and the external electrodes of the connecting subject are connected with each other through the electrically conductive members, the electric connection between both the electrodes can be made more reliable.
(11) According to another aspect of the present invention, there is provided a method for connecting electrodes, by which terminal electrodes formed in a narrow-pitch connector having a pitch converting function are respectively connected with external electrodes formed in a connecting subject; wherein heating conditions are established on the basis of a difference in thermal expansion coefficient between the narrow-pitch connector and the connecting subject, and an area where the terminal electrodes are connected with the external electrodes respectively is pressed and heated.
(12) According to another aspect of the present invention, in the electrode connection method stated in the above paragraph (11), the above mentioned area is heated by a first heater and a second heater from the side of the terminal electrodes and the side of the external electrodes respectively under the aforementioned heating conditions.
In the aforementioned inventions (11) and (12), if the connecting subject is different, the thermal expansion coefficient thereof becomes different. Therefore, heaters are provided on the terminal electrode side and on the external electrode side independently of each other. These heaters are controlled under heating conditions based on the difference in thermal expansion coefficient between the narrow-pitch connector and the connecting subject. Thus, one of the connecting subjects having a smaller thermal expansion coefficient is put on the side of high temperature while the other connecting subject with a higher thermal expansion coefficient is put on the side of low temperature. Then, the temperature difference between the connecting subjects is set so that the distance between the terminal electrodes in one connecting subject is equal to that in the other. As a result, the distance between the terminal electrodes formed in one connecting subject can be made equal to that in the other. Therefore, the terminal electrodes can be connected with each other reliably even if the connecting subjects have different thermal expansion coefficients.
(13) According to another aspect of the present invention, there is provided a micro-machine comprising a moving mechanism portion and a first substrate in which a plurality of first terminal electrodes are formed; wherein: the micro-machine is provided with a second substrate in which second terminal electrodes for making an electric connection with the plurality of first terminal electrodes are formed; a plurality of third terminal electrodes and wiring for electrically connecting the second terminal electrodes with the third terminal electrodes respectively are formed on the second substrate; and the wiring has a function of making a conversion from a pitch of the second terminal electrodes to a pitch of the third terminal electrodes.
In the aforementioned invention (13), in the micro-machine, the first substrate in which the moving mechanism portion of the micro-machine is formed and the second substrate for making a connection with the outside are formed separately. Accordingly, the area of the first substrate can be minimized.
(14) According to another aspect of the present invention, there is provided a piezoelectric actuator comprising a piezoelectric element and a first substrate in which a plurality of first terminal electrodes are formed; wherein: the piezoelectric actuator is provided with a second substrate in which second terminal electrodes for making an electric connection with the plurality of first terminal electrodes are formed; a plurality of third terminal electrodes and wiring for electrically connecting the second terminal electrodes with the third terminal electrodes respectively are formed on the second substrate; and the wiring has a function of making a conversion from a pitch of the second terminal electrodes to a pitch of the third terminal electrodes.
(15) According to another aspect of the present invention, there is provided an electrostatic actuator comprising an electrostatic vibrator and a first substrate in which a plurality of first terminal electrodes are formed; wherein: the electrostatic actuator is provided with a second substrate in which second terminal electrodes for making an electric connection with the plurality of first terminal electrodes are formed; a plurality of third terminal electrodes and wiring for electrically connecting the second terminal electrodes with the third terminal electrodes respectively are formed on the second substrate; and the wiring has a function of making a conversion from a pitch of the second terminal electrodes to a pitch of the third terminal electrodes.
(16) According to another aspect of the present invention, there is provided an ink jet head comprising a piezoelectric element and a first substrate in which a plurality of first terminal electrodes are formed, so as to discharge ink drops by the piezoelectric element; wherein: the ink jet head is provided with a second substrate in which second terminal electrodes for making an electric connection with the plurality of first terminal electrodes are formed; a plurality of third terminal electrodes and wiring for electrically connecting the second terminal electrodes with the third terminal electrodes respectively are formed on the second substrate; and the wiring has a function of making a conversion from a pitch of the second terminal electrodes to a pitch of the third terminal electrodes.
(17) According to another aspect of the present invention, there is provided an ink jet head comprising an electrostatic vibrator and a first substrate in which a plurality of first terminal electrodes are formed, so as to discharge ink drops by the electrostatic vibrator; wherein: the ink jet head is provided with a second substrate in which second terminal electrodes for making an electric connection with the plurality of first terminal electrodes are formed; a plurality of third terminal electrodes and wiring for electrically connecting the second terminal electrodes with the third terminal electrodes respectively are formed on the second substrate; and the wiring has a function of making a conversion from a pitch of the second terminal electrodes to a pitch of the third terminal electrodes.
(18) According to another aspect of the present invention, there is provided an ink jet printer comprising an ink jet head having a piezoelectric element and a first substrate, the first substrate being provided with a plurality of first terminal electrodes formed therein; wherein: the ink jet printer is provided with a second substrate in which second terminal electrodes for making an electric connection with the plurality of first terminal electrodes are formed; a plurality of third terminal electrodes and wiring for electrically connecting the second terminal electrodes with the third terminal electrodes respectively are formed on the second substrate; and the wiring has a function of making a conversion from a pitch of the second terminal electrodes to a pitch of the third terminal electrodes.
(19) According to another aspect of the present invention, there is provided an ink jet printer comprising an ink jet head having an electrostatic vibrator and a first substrate, the first substrate being provided with a plurality of first terminal electrodes formed therein; wherein: the ink jet printer is provided with a second substrate in which second terminal electrodes for making an electric connection with the plurality of first terminal electrodes are formed; a plurality of third terminal electrodes and wiring for electrically connecting the second terminal electrodes with the third terminal electrodes respectively are formed on the second substrate; and the wiring has a function of making a conversion from a pitch of the second terminal electrodes to a pitch of the third terminal electrodes.
In the aforementioned inventions (14), (16) and (18), the first substrate in which a piezoelectric element is formed and the second substrate for making a connection with the outside are formed separately. Accordingly, the area of the first substrate can be minimized.
On the other hand, in the aforementioned inventions (15), (17) and (19), the first substrate in which an electrostatic vibrator is formed and the second substrate for making a connection with the outside are formed separately. Accordingly, the area of the first substrate can be minimized.
(20) According to another aspect of the present invention, there is provided a liquid crystal device in which a liquid crystal is held between a first substrate and a second substrate, and a plurality of first terminal electrodes are formed on either the first substrate or the second substrate; wherein: the liquid crystal device is provided with a third substrate in which second terminal electrodes for making an electric connection with the plurality of first terminal electrodes are formed; a plurality of third terminal electrodes and wiring for electrically connecting the second terminal electrodes with the third terminal electrodes respectively are formed on the third substrate; and the wiring has a function of making a conversion from a pitch of the second terminal electrodes to a pitch of the third terminal electrodes.
In the aforementioned invention (20), the so-called liquid crystal cell in which the liquid crystal is held between the first substrate and the second substrate and in which a plurality of first terminal electrodes are formed in one of the first and second substrates, and the third substrate for making a connection with the outside are formed separately. Accordingly, the area occupied by the first terminal electrodes in the liquid crystal cell can be minimized. Therefore, a large liquid crystal display portion can be ensured in the liquid crystal cell even if the liquid crystal cell having the same area as that in a background-art is used. In addition, because the number of terminals in a connecting portion can be increased easily, the pitch of picture elements can be reduced so that the picture elements can be made precise extremely.
(21) According to another aspect of the present invention, there is provided an electronic equipment comprising a liquid crystal device; wherein the liquid crystal includes a first substrate and a second substrate so that a liquid crystal is held between the first substrate and the second substrate, either the first substrate or the second substrate being provided with a plurality of first terminal electrodes, and further include a third substrate in which second terminal electrodes for making an electric connection with the plurality of first terminal electrodes are formed; a plurality of third terminal electrodes and wiring for electrically connecting the second terminal electrodes with the third terminal electrodes respectively are formed on the third substrate; and the wiring has a function of making a conversion from a pitch of the second terminal electrodes to a pitch of the third terminal electrodes.
In the aforementioned invention (21), the liquid crystal device in the electronic equipment is configured so that the liquid crystal is held between the first substrate and the second substrate, and the so-called liquid crystal cell in which a plurality of first terminal electrodes are formed in one of the first and second substrates, and the third substrate for making a connection with the outside are formed separately. Accordingly, the area occupied by the first terminal electrodes in the liquid crystal cell can be minimized. As a result, miniaturization of the electronic equipment becomes easy.